The additional images on the product detail page, when you click on one thumbnail, the huge photo opens with horizontal scrollbars and all. Clicking on the back-button in the browser results in going to the previous page (not the detail page, but the page before that!). To avoid that I open the additional images in a modal window. So the user can see the enlarged image and close it without losing the page. For consistency I added the main image in the thumbnails as well (and override the default_images.php template to not link to the max size photo).

(obviously I made the modifications in a template override, but here is the original file)file:components/com_virtuemart/views/productdetails/default_images_additional.phpline: 24